Since the VCE was introduced 19 years ago, mid-year exams have been held in accounting, biology, chemistry, environmental science, physics and psychology.

The results of the June exams contribute up to 33 per cent of students' final marks in these subjects.

However, Victorian Curriculum and Assessment Authority chief executive officer John Firth said principals had called for changes given less than half of VCE students did subjects that had mid-year exams.

''Principals have been saying the school year is very tight and lots of students don't have mid-year exams but everything stops for those who do,'' Mr Firth said.

He said from 2013 exams for all VCE students would be aligned.

Under the changes there will be a 2½-hour exam in November in biology, chemistry, physics and psychology. Two-thirds of students' scores will be based on their exam results and one-third on their school-assessed coursework.

In accounting and environmental science there will be a two-hour exam at the end of the year, which will make up half of students' results.

Tim O'Neill, who did VCE at Sunshine College this year, said scrapping mid-year exams would put more pressure on students, who would be tested on a full year's work in November, rather than only six months.

The final exam would also contribute 66 per cent to overall scores, rather than 33 per cent.

Tim said sitting mid-year exams in biology and psychology prepared him for the final exams and made him feel more optimistic.

''You know what you are in for at the end of the year,'' he said.

However, Ringwood Secondary College principal Michael Phillips supported the changes because teachers would not have to suspend their teaching program to enable students to revise for mid-year exams.

He said the Victorian Curriculum and Assessment Authority needed to look at other ways of improving VCE assessments.

Meanwhile, the authority has published an apology in its latest bulletin to Melbourne writer Helen Razer for ''our failure to acknowledge her moral rights as author of an article that was adapted for use in the 2011 VCE English examination''.

The English exam featured an Age column on tattoos by Ms Razer without her permission and falsely attributed the article to ''part-time journalist and blogger Helen Day'', who wrote for the blog ''Street Beat''.

''We apologise for failing to attribute her as the source of the article, for falsely attributing authorship and for making changes to her original article without her authorisation,'' the apology says.

''The VCAA Board and CEO have commissioned an external review of its procedures for using published works in all examinations in the future.''